Since he had said bigger injectors I hadn't mentioned this, but you're right - fuel getting returned to the tank can really affect things. I just had a truck in here today that had "new" injectors installed by a shade tree mechanic (took 4.5 MONTHS
) and when they got it back it had an injector knocking. While checking balance rates and disabling injectors to narrow it down I also played with pressure and the truck would only build up to 15K PSI. After swapping out the one bad injector and re-checking the balance rates and all the truck would hold the commanded 23K PSI at idle all day long. I didn't expect one bad injector to be able to drain rail pressure that badly.